An exhaust gas recirculation system may be used to reduce the generation of undesirable pollutant gases during the operation of internal combustion engines. Exhaust gas recirculation systems generally recirculate exhaust gas generated during the combustion process into the intake air supply of the internal combustion engine. The exhaust gas introduced into the engine cylinders displaces a volume of the intake air supply that would otherwise be available for oxygen. Reduced oxygen concentrations lower the maximum combustion temperatures within the cylinders and slow the chemical reactions of the combustion process, which decreases the formation of oxides of nitrogen (NOx).
Many internal combustion engines having such an exhaust gas recirculation system also have one or more turbochargers. Exhaust gas from the combustion cylinders is typically used to drive the turbocharger of the turbocharger which, in turn, drives the compressor of the turbocharger to compress fluid that is subsequently supplied to the combustion cylinders. A portion of the exhaust gas may also be diverted from the exhaust system used to drive the turbocharger and into the exhaust gas recirculation system.
EGR flow measurement has been attempted in the past. For example, U.S. Patent Application No. US 20100145598A1 discloses an exhaust gas recirculation measurement system wherein the total gas flow of the engine is calculated by measuring temperature and pressure at the engine intake. The fresh airflow is measured by a venturi in the flow path for fresh air for combustion by the engine prior to the introduction of the EGR flow. The difference between the calculated total flow and fresh airflow is the actual EGR flow which is used to set the EGR relative to total flow.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.